Let Compass Plant Show You the Way!
Written and researched by Mary Nelson
Do you really need a GPS to get you to your location or could you just use the compass plant to point you in the right direction? Early pioneers used the compass plant to guide themselves on their journey west, particularly at night when they could not rely on the sun for direction. The name compass plant comes from the observation that the large leaves are held vertically with their tips pointing north or south and the upper and lower surfaces facing east and west. While it would be nice to think that the plants do this to help poor lost souls find their way, the real reason is to maximize exposure of the leaves to morning and afternoon sun while reducing the effect of full mid-day sun. This allows the plants to maximize water use as well as to increase carbon dioxide gain for photosynthesis.
Photo by Mary Nelson
I am a fan of numerous native plants and compass plant (Silphium laciniatum) is one of my favorites. From its beautiful leaves to its imposing height, it is downright impressive! The leaves are large and deeply lobed. They occur at the base of the plant and may be upwards of 20 inches long and about 10 inches across at their widest point. When the leaves first develop, they are arranged randomly. However, within 2 to 3 weeks, the leaves will assume their north-south orientation. When mature, compass plant will bloom from July well into September. The plant will produce numerous sunflower-like blooms along stems that can grow to 10 feet tall. Since there can be numerous stems on a mature compass plant, the floral display can be breathtaking. The composite flowers are about 2 to 3 inches in diameter, with yellow ray flowers (petals) and a central yellow head composed of disk flowers. In most flowers with this structure, seeds are produced by the central disk flowers. With compass plants, however, the disk flowers are sterile, and seeds are produced by the ray flowers (petals). The flowers of compass plant attract bees, butterflies and other pollinators, and the seeds are a favorite among birds in the fall.
Compass plant is native to southern Wisconsin where it is a staple in tall grass prairies. It is also a great addition to native wildflower gardens, including shoreline gardens, throughout the state. It should be planted in a location with full sun with dry to medium moisture soil. Avoid slopes since the plants will tend to flop when planted on uneven ground. Compass plants are not picky about soil type and will grow well in sand, loam, or clay. Make sure to allow it a space that is three feet in diameter since the plant will get wider as it develops more leaves and new stems. Choose your location wisely since the compass plant quickly establishes a deep tap root that will ultimately extend down into the soil 12 to 15 feet, making it nearly impossible to move. This deep tap root makes the plant very drought tolerant and able to withstand temporary poor conditions such as drought or flooding. It may also be part of the reason that, under the right conditions, compass plants can live up to 100 years. Compass plant spreads by seed but does not spread vegetatively, meaning it will not send out rhizomes and pop up a new plant every foot or so like plants such as common milkweed (Asclepias syriaca).
You should give compass plant a try. I guarantee that people who see it will be impressed with its regal stature, and you will enjoy telling them all about its amazing qualities. Here’s one last fact about compass plant. Native Americans used the bitter resin from broken stems as a mouth-cleansing chewing gum. While a fun fact to share, I certainly would not recommend giving it a try.
Mary’s bio:
After retiring from a career in laboratory medicine, Mary decided it was time to refocus and became a Master Gardener. Not knowing exactly what she wanted to go as a gardener, she dabbled in everything. It was not until she attended a pollinator workshop in 2012 that she discovered her passion for pollinators. This, of course, included a passion for native plants as well. Since that time, Mary has started thousands of native Wisconsin plants from seed, done presentations on how to support pollinators, helped homeowners establish pollinator gardens in their backyards, and sponsored native plant sales for various organizations. At their home in southern Wisconsin, Mary and her husband Roger sustain a 25-acre tallgrass prairie and numerous smaller “groomed” pollinator gardens. Mary has also covered the shoreline of their vacation home in northern Wisconsin with native plants to support all sorts of pollinators and to protect water quality.
Photo by Marci Hess